Orbital torque switching of perpendicular magnetization in Ti/ferrimagnet bilayers

<p>Orbital torque, associated with orbital current, enables light metals to efficiently manipulate magnetization with rich tunability. A clear demonstration of perpendicular magnetization switching using light metals alone is essential for understanding orbital physics and developing high-density orbitronic devices. Here, we report orbital torque switching of perpendicular magnetization of ferrimagnet (Fe<sub>1-x</sub>Gd<sub>x</sub>) using Ti 3d light metal alone. The torque efficiency increases four-fold by enhancing the spin-orbit coupling in Fe<sub>1-x</sub>Gd<sub>x</sub> through modulating Gd composition, which is a characteristic feature of orbital torque. Our findings demonstrate that light metals in combination with rare earth-transition metal ferrimagnets can be employed for efficient orbitronic devices and serve as a model system for studying orbitronics.</p>